i40e/base: enhance NVM checksum calculation
i40e/base: enhance NVM checksum calculation

The data buffer for i40e_calc_nvm_checksum() is too big, so move
it off and allocate separately. In addition, use
i40e_read_nvm_buffer() to get the whole shadow RAM, together with
minor enhancements.

Test report: http://www.dpdk.org/ml/archives/dev/2015-May/017384.html

Signed-off-by: Helin Zhang <aba9dfdb1a6ec8bf1ff66b95272c029f8dfde1b1@intel.com>
Acked-by: Jijiang Liu <10b95deab7df654d0c21c8c98b54c9a1ecf2a5c0@intel.com>
Tested-by: Min Cao <2a88aab028744885054f990971530d20553769a9@intel.com>

john-mcnamara-intel/dpdk,venkynv/dpdk-mirror,mixja/dpdk,tsphillips/dpdk-fork,msune/dpdk,venkynv/dpdk-mirror,john-mcnamara-intel/dpdk,mixja/dpdk,venkynv/dpdk-mirror,mixja/dpdk,john-mcnamara-intel/dpdk,venkynv/dpdk-mirror,mixja/dpdk,tsphillips/dpdk-fork,tsphillips/dpdk-fork,msune/dpdk,tsphillips/dpdk-fork,msune/dpdk,john-mcnamara-intel/dpdk,msune/dpdk